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What is an ISBN?

An ISBN, or International Standard Book Number, is a 13-digit identifier for one format of one book. The publisher applies for it through a national ISBN agency. It identifies the book but gives no copyright or legal protection, and each format, such as a paperback or an EPUB, gets its own.

What it means in practice

KDP offers a free ISBN for paperbacks and hardcovers. It can’t be used anywhere else, and the book’s imprint then reads “Independently published”. If you want to name your own imprint or print elsewhere, apply for your own ISBN through your country’s agency.

An ISBN doesn’t protect the book. The international agency’s words are that it “does not convey any form of legal or copyright protection”.

How Chapbook uses it

Edit details has an optional ISBN field, with the hint “Only if you bought one; stores issue their own.” Chapbook writes it into the EPUB’s metadata beside the book’s own identifier, and nowhere else: the copyright page of the PDF and Word document does not print it, and the paperback’s back cover leaves the barcode to KDP.

Because each format has its own ISBN, don’t reuse one you bought for the paperback in this field.

In a real book

Cover of The Pricing Playbook by Jane Founder: a brass balance scale lit from the left on deep teal above white type, subtitle “How founders set a price they can defend”.
Title page. Page 1 of The Pricing Playbook.
Copyright. Page 2 of The Pricing Playbook.
Contents. Page 3 of The Pricing Playbook.
Introduction. Page 4 of The Pricing Playbook.
Introduction. Page 5 of The Pricing Playbook.
Why Guessing Fails. Page 6 of The Pricing Playbook.
Why Guessing Fails. Page 7 of The Pricing Playbook.
Why Guessing Fails. Page 8 of The Pricing Playbook.
Why Guessing Fails. Page 9 of The Pricing Playbook.
What You Are Actually Selling. Page 10 of The Pricing Playbook.
What You Are Actually Selling. Page 11 of The Pricing Playbook.
What You Are Actually Selling. Page 12 of The Pricing Playbook.
What You Are Actually Selling. Page 13 of The Pricing Playbook.
Interview Ten Customers. Page 14 of The Pricing Playbook.
Interview Ten Customers. Page 15 of The Pricing Playbook.
Interview Ten Customers. Page 16 of The Pricing Playbook.
Interview Ten Customers. Page 17 of The Pricing Playbook.
Interview Ten Customers. Page 18 of The Pricing Playbook.
Choose the Value Metric. Page 19 of The Pricing Playbook.
Choose the Value Metric. Page 20 of The Pricing Playbook.
Choose the Value Metric. Page 21 of The Pricing Playbook.
Choose the Value Metric. Page 22 of The Pricing Playbook.
Draft Three Tiers. Page 23 of The Pricing Playbook.
Draft Three Tiers. Page 24 of The Pricing Playbook.
Draft Three Tiers. Page 25 of The Pricing Playbook.
Draft Three Tiers. Page 26 of The Pricing Playbook.
Set the Numbers. Page 27 of The Pricing Playbook.
Set the Numbers. Page 28 of The Pricing Playbook.
Set the Numbers. Page 29 of The Pricing Playbook.
Set the Numbers. Page 30 of The Pricing Playbook.
Say the Price Out Loud. Page 31 of The Pricing Playbook.
Say the Price Out Loud. Page 32 of The Pricing Playbook.
Say the Price Out Loud. Page 33 of The Pricing Playbook.
Say the Price Out Loud. Page 34 of The Pricing Playbook.
Revisit Every Quarter. Page 35 of The Pricing Playbook.
Revisit Every Quarter. Page 36 of The Pricing Playbook.
Revisit Every Quarter. Page 37 of The Pricing Playbook.
Revisit Every Quarter. Page 38 of The Pricing Playbook.
Conclusion. Page 39 of The Pricing Playbook.
Conclusion. Page 40 of The Pricing Playbook.
Appendix: The Interview Script. Page 41 of The Pricing Playbook.
Appendix: The Interview Script. Page 42 of The Pricing Playbook.
Back cover of The Pricing Playbook: the description over the cover's artwork.
Introduction 5 / 44
The Pricing Playbook, how founders set a price they can defend: a nonfiction book of 9,862 words and 43 pages on 6 × 9 in, generated from one brief and exported unedited. It is a sample, not a customer's book. Download the PDF (381 KB) or the EPUB (107 KB).

Sources

Last reviewed 30 October 2026

  1. International ISBN Agency, “What is an ISBN?”
  2. Amazon KDP, “What is an ISBN and Imprint Name?”
  3. Amazon KDP, “What is an ISBN and Imprint?”
  1. What is an ASIN on Amazon? An ASIN, Amazon Standard Identification Number, is the identifier Amazon gives each book it lists. How it differs from an ISBN, and what you do with one.
  2. What is a BISAC code? BISAC subject codes are the US book trade's standard topic categories. What a code looks like, how many to use, and how they relate to KDP's own categories.
  3. What is Kindle Direct Publishing (KDP)? Kindle Direct Publishing is Amazon's free self-publishing service for eBooks, paperbacks and hardcovers. What it asks for, and what Chapbook prepares for it.

Questions people ask

Do I need an ISBN to publish on KDP?

For a paperback or hardcover, yes. For an eBook, no: KDP's help page, checked on 30 October 2026, says eBooks don't require one, and it assigns an ASIN instead.

Can I use a free KDP ISBN at another printer?

No. KDP says its free ISBNs can only be used on KDP and cannot be used to publish outside it. The imprint on one reads “Independently published”.

Does Chapbook need an ISBN?

No. The field is optional and none of Chapbook's files needs one. Fill it in only if you already have an ISBN for the EPUB.

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